Metallized cutlery and tableware and method therefor

ABSTRACT

A plastic cutlery item molded from a plastic material, such as polystyrene, having a metallic coating that imparts to this cutlery item the appearance of metal cutlery or silverware. In one embodiment the plastic cutlery or tableware items are molded using injection molding techniques, and subjected to a vacuum metallizing process in an individualized non-contiguous manner, where a thin metallic layer is deposited on at least one of their surfaces. The resultant items simulate the appearance of metal cutlery or tableware. In one embodiment of the invention the plastic cutlery or tableware articles are molded from a clear polystyrene resin and are coated with a thin stainless steel layer through vacuum sputtering deposition on only one of the sides. The abrasion resistance of the metallic coating can be enhanced by subjecting the articles to a post-metallizing holding period or by applying a clear protective overcoat.

RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 10/228,147, filed Aug. 26, 2002, which, in turnclaims the benefit of U.S. Provisional Patent Application Ser. No.60/314,677, filed Aug. 24, 2001; said applications are incorporatedherein, in entirety, by reference for all purposes.

FIELD OF THE INVENTION

This invention relates generally to the production of food-servicearticles for household, catering and restaurant use including commercialand institutional tableware. More particularly, this invention relatesto plastic cutlery having a reflective or metallic appearance.

BACKGROUND OF THE INVENTION

Disposable plastic food-service items are in increasingly widespread usefor storing, serving and consuming food, due to their reasonablylow-cost and the convenience they provide. Disposable food containersand articles inter alia include non-returnable containers such as yogurtcups and dinner entree packaging; microwavable storage containers; and,general tableware items such as plastic plates, cups and cutlery. Theincreasing popularity of fast-food restaurant chains further fuels thedemand for plastic tableware and takeout packaging. In addition to thefast food restaurants, caterers also prefer disposable food serviceitems for the associated convenience, hygiene and competitive-costs. Inthis regard, it is important to note that replacement costs fordisposable items such as cutlery articles are usually offset by clean-upcosts (labor, materials and equipment) generally associated withpermanent flatware. In addition, permanent flatware also has to bereplaced due to inadvertent disposal or loss.

The presence of non-disposable metal cutlery along with other disposablefood-service articles such as plates, cups and the like presents anunusual problem for restaurants and caterers. The problem stems from theloss of valuable metal cutlery into trash or refuse-containers alongwith disposable tableware and food remnants particularly during peakbusiness hours and rush situations. As a result, the food establishmenthas to constantly replace expensive metal flatware. There has been along-standing need to solve the problems relating to loss andinadvertent disposal of real silverware, as readily evidenced by thefollowing excerpts taken from the patent literature:

U.S. Pat. No. 3,926,792, to Buford, filed on Aug. 23, 1973, in Column 1,lines 12 to 30 states:—“The food industry has long been plagued with thecostly and time-consuming problem of separating valuable reusable items,such as metal tableware from solid waste, such as food, paper and otherdisposable items. This problem is prevalent in any food servicefacility, such as restaurants, cafeterias, schools, prisons, and so on,in which plates must be scraped and/or tableware separated from garbageby hand sorting or by scavenging, and especially in the airline industrywhere there is no opportunity for sorting in flight. Even when manualsorting or scavenging is carried out, it has been found that a largeamount of tableware is lost. For example, a set of airline tablewareonly lasts about seven flights. It is obvious that continued replacementof tableware is not only expensive, but economically wasteful. Somerestaurants have found that most missing tableware is lost, rather thantaken by customers, and that such losses run as high as $1,300 on atraditionally heavy day.”

U.S. Pat. No. 4,367,138, to Kustas, filed on Jun. 8, 1981, in Column 1,lines 11-16 states:—“ . . . . As is well-known in the restaurantbusiness, the loss of silverware or stainless steel flatware is a veryserious problem which costs restaurant owners large sums of money everyyear. The problem stems from careless kitchen help and the manner inwhich food and debris is removed from used dishes.”

U.S. Pat. No. 4,632,253, to Stromgren et al., filed on Dec. 6, 1984, inColumn 1, lines 35-49 states:—“In conjunction with a waiter scrappingfood waste from plates into a waste container, it quite often happensthat cutlery accompanies the waste into the container. For obviousreasons, the waiter avoids putting his arm down into the waste containerto retrieve the dropped item. Studies made in restaurant kitchens inhotels associated with several intercontinental hotel chains show thatnot only an occasional item of cutlery is lost in this way, but even thecutlery used by all the guests at a table may be accidentally tippedinto the waste container together with waste food, particularly when therestaurant is busy and the waiter rushed. It must be regarded as naturalthat the waiter also avoids taking up the cutlery dropped into the wastecontainer in such circumstances.”

In addition, market research conducted by Waddington North America,Inc., the assignee of the present invention, shows that caterersestimate a loss of 15% to 30% of permanent flatware annually.

Another problem that food caterers encounter is the ability to cleanmetal flatware utensils at certain locations and outdoor cateringevents. In preparation for such circumstances caterers tend to carry alarge inventory of expensive metal cutlery. The use of disposableplastic cutlery for such catering events would eliminate the limitationswith cleaning metal flatware, handling heavy metal cutlery or keeping alarge inventory thereof. In addition, it is noteworthy that disposablecutlery offers significant handling advantages compared to itsmetal-counterparts. For example, a typical cutlery combinationcontaining a fork, a knife, a tablespoon, and a teaspoon would weighabout 200 grams for metal flatware versus about 30 grams for premiumplastic cutlery. Applying these weights to a hypothetical 250-personevent would yield an overall weight for metal cutlery of about 110 lbs.,as compared to only 16 lbs. for plastic cutlery.

After the tragic 9-11 terrorist attacks with hijacked airplanes and thepotential threat resulting from misuse of stainless steel flatware asweapons, there has been an increased tendency for major airlineorganizations to utilize disposable plastic cutlery while serving mealsduring flights. However, the use of disposable plastic cutlery affectsthe image of the airline, especially in premium seating and higherpriced flights. What is lacking in the industry is a silverware articlethat is authentic looking yet is made of plastic would allow theAirlines to preserve their upscale image, particularly in the premiumpassenger classes, while continuing to enhance flight safety andmaintaining compliance with legal and regulatory mandates.

A significant number of upscale catering establishments utilizedisposable plastic cups, plates, and bowls etc. for catering functions.However, there is a general preference for continued use of traditionalmetal cutlery, primarily because of a perception gap between disposableplastic cutlery articles and permanent flatware. Disposable cutleryarticles are generally regarded as having less-than-classic appearanceand not suited for an upscale presentation; while, permanent flatware isgenerally regarded as more upscale and having a superior image. Thisperception gap is not entirely due to the superior strength of permanentflatware. Although stainless steel cutlery or permanent flatware isstronger than plastic cutlery, heavy weight plastic cutlery isfunctionally adequate for most occasions. Thus, a primary obstacle foruse of disposable plastic cutlery in upscale situations is theperception and the image associated with disposable plastic cutleryrather than its performance.

From the foregoing, it can be readily appreciated, that there is a needfor cutlery and food-handling implements that offer the disposabilityand convenience of plastic cutlery and the upscale perception generallyassociated with permanent flatware. Bridging the perception gap betweendisposable plastic cutlery and permanent flatware would naturally leadto greater acceptance of disposable plastic cutlery for use in upscalesituations, by caterers and other food-service establishments, wheretraditionally permanent flatware heretofore has been the onlyalternative.

With respect to plastic articles, there are a variety of methods forcoloring and/or decorating plastic articles that have been employed inthe art including—dyeing, pigmenting, printing, hot stamping, heattransfers, in-mold decorating, spray painting, and electroplating.Printing techniques have been further classified as silkscreen printing,gravure or offset printing, and pad transfer printing.

Coloring or pigmenting is one of the most common and inexpensive methodsto modify or enhance the appearance of a plastic article. Coloringtypically involves incorporating a pigment or a dye into the plasticresin that is used for molding plastic articles. Pigments can be in theform of solid color concentrates or in the form of liquid color.Metallic pigments are known in the art and are commercially available;however, it is the general experience of those skilled in the art thatthese metallic pigments do not impart an authentic metallic look.Furthermore, metallic pigments do not provide a plastic cutlery articlethat emulates the polished silver-like metallic appearance of finecutlery or silverware. In fact, almost all commercial plastic tablewareor cutlery articles made by utilizing a silver metallic pigment have adull or grayish appearance. In addition, some of the formulations formetallic pigments have an odor which is less-than-desirable for afood-service item.

Printing with single or multi-colored inks is commonly used fordecorating plastic articles. The types of inks that can be used withfood service articles tend to be limited due to food contact, toxicityand environmental issues. In addition, at least some of the inksfrequently require a protective overcoat to overcome food contactissues. Metallic inks are known in the art; however, metallic inks alsohave similar food contact drawbacks and are not adapted for use withfood handling implements due to a variety of reasons. Firstly, it wouldbe difficult to handle the three-dimensional shape of a fork or a spoonand to apply a uniform layer of metallic ink thereon in an economic orconsistent manner. Secondly, metallic inks do not provide thecharacteristic reflective appearance of a polished stainless steelflatware item or similar metallic article. Thirdly, the appearance ofmetallic inks would be further marred by the necessity of adding aprotective overcoat for safety and food contact purposes.

In-mold labeling or decorating refers to the technique for decorating aplastic article wherein a label is strategically placed inside the moldprior to molding and held against a mold face by vacuum or mechanicalmeans, thereafter hot plastic resin is introduced into the mold toeffect label adhesion onto the molded part; and, thereby the label andthe molded part are integrated into a unified article. Although, it isconceivable that a metallic label can be devised for use in injectionmolding, in-mold labeling is mostly limited for parts that either have aplanar surface or a smooth curved surface such as the outer wall of acup. In-mold labeling is not readily or economically adaptable forarticles having complex three dimensional shapes such as typical spoonsor forks. In addition to general shape constraints, in-mold labelingoperation on a cutlery article would further prove to be quitechallenging due to the presence of ornate features or fine and intricatepatterns frequently incorporated on the surface of a plastic cutleryarticle for commercial acceptance and in consistency with traditionalflatware design trends. It would be readily recognized by those ofordinary skill that the presence of any delicate design features on thesurface of the article would interfere with in-mold label adhesion,which in turn would lead to wrinkling of the label on the part surfaceand detract from the overall appearance of the cutlery article.

Heat transfers and hot-stamping techniques provide additional optionsfor decorating plastic articles. In particular, metal foil stamping canprovide an authentic metallic-look when strategically placed on aplastic surface. Once again these techniques are not suited for articleshaving complex three-dimensional geometry such as cutlery articles. Foilwrinkling and/or inconsistent adhesion in the intricate detail areas ofa cutlery article limit the utility of the foil stamping process forobtaining disposable cutlery having the appearance of permanent flatwareor authentic silverware.

Electroplating methods for metallizing plastic cutlery articles areundesirable due to the environmental impact associated withelectroplating chemicals as is known in the art. In addition, not allplastics can be readily electroplated. Furthermore, electroplatingoffers several challenges in terms of handling and processing cutleryarticles economically.

Various metallizing methods have been described in the art, includingU.S. Pat. No. 5,022,554 that describes metallized tableware, such asplates, cups, etc., made of a paper substrate, a metallized plastic filmjoined to the substrate, and an FDA approved top coating over theplastic film. This method of obtaining a metallic-look food serviceitems by laminating a metallized film is not readily applicable tocutlery due to the fact that most plastic cutlery is generally producedby the injection-molding process wherein the feedstock is thermoplasticresin pellets and not laminated film. The shortcomings of incorporatinga metallic foil or label during injection molding plastic cutlery havebeen discussed herein above. Similar shortcomings would typically applyto the use of a laminated metallic film.

Other approaches to metallization such as those used by Quest et al.(U.S. Pat. Nos. 5,177,124 and 5,280,052) describe a utilitarian and/ordecorative object and a method for forming plastic parts having ametallic outer face, appearance and hand. In this technique, a mixtureof a liquid monomer, curing agent, a dispersion of metal particles andfloatable particles are poured into a mold. The mold is then centrifugedto cause the metal particles to migrate towards the surface of the piecebefore the monomer polymerizes and hardens to bind the particles. Afterremoval from the mold, the outer face of the piece is polished andbuffed to remove the plastic skin from the metal surface, whereby theresultant plastic piece simulates the appearance of a solid metal piece.This method is generally too cumbersome for application to plasticcutlery as most plastic cutlery is either made of polystyrene and/orpolypropylene which are thermoplastic polymeric materials and do noteasily lend themselves to the teachings of the referenced art. Inaddition, the typical process for producing cutlery is injection moldingand it is difficult and cost-prohibitive to rotate a heavy injectionmold. And, finally the secondary step of cleaning and buffing theplastic piece is expensive and may be unacceptable for food-service use.

Various references are available on plating of plastic materials bychemical deposition techniques, electro-deposition techniques and/or acombination thereof. Some plating methods are described in U.S. Pat.Nos. 3,607,350; 3,629,922; 3,896,252; 3,962,494; 4, 4,610,895;3,445,350; 4,039,714; 4,073,743; 4,195,117; and 4,810,333. Thesetechniques are essentially wet processes and require that parts bebrought into contact with solutions containing metal ions, which mustthen be washed off to remove any residual chemicals and for generalhygiene reasons for a food service article. These processes arerelatively unattractive for metallizing cutlery because of the highprocessing and environmental costs.

Thus, it can be readily established that there is a need for fineplastic cutlery that has an enhanced visual and commercial appeal. Theimproved plastic cutlery should be inexpensive, permitting simpledisposal and not requiring separation from food refuse. Such aninvention should be manufactured without environmental shortcomingsgenerally associated with metal-plating wet processes. An improvedplastic cutlery article should be fabricated primarily from plasticmaterials, yet have the appearance of genuine metal on the outer surfacesuch that it is practically indistinguishable, at least visually, from afine metal flatware or cutlery article.

SUMMARY OF THE INVENTION

The present invention is devised in the light of the problems describedherein. Accordingly it is a general object of the present invention toprovide cutlery or flatware items that can (a) solve problems associatedwith present techniques for enhancing the visual appeal and upscaleimage of disposable plastic cutlery; (b) address the specific long-feltneed for solving problems related to inadvertent loss and disposal ofpermanent flatware at restaurants and catering events; and (c) bridgethe perception gap between disposable plastic cutlery and permanentflatware. In one aspect of the invention these needs are met byimparting a metallic appearance to disposable plastic cutlery orflatware articles.

The present invention was derived in-part from the recognitionthat—imparting a metallic appearance to disposable plastic cutlery wouldenhance the perceived value and quality of the cutlery items and bridgethe perception gap between plastic cutlery and permanent flatware.

The same is true for the additional tableware items such as cups andplates. Employing a metallic appearance such as gold or silver to theplates and cups to coordinate with the cutlery enhances the aestheticsand provides a more regal presentation. The state of the art generallydoes not introduce metallized plastic cups and plates due to thedifficulties discussed herein. Thus while the present descriptionfocuses on cutlery, the information is also relevant to other tablewareitems and is within the scope of the present invention.

One of the objects of the invention is to provide premium disposablecutlery item(s) fabricated mainly from plastic materials and having ametallic surface appearance that simulates genuine metal or permanentflatware.

Yet another object of the present invention is to provide a method,which lends itself to mass production of plastic cutlery having anauthentic metallic appearance at a reasonable cost for disposable use.

Still another object of the present invention is to provide a method formetallizing injection-molded plastic cutlery at a reasonable incrementalcost.

A further object of the present invention is to provide disposablecutlery that has the appearance of fine metal cutlery.

A further object of the present invention is to obtain a plastic object,such as a cutlery item, which is molded from a light transmittingthermoplastic material and is subsequently metallized.

Another object of the present invention is to provide a method formetallizing plastic cutlery articles that obviates the need for coatingarticles on both sides for emulating metal silverware.

Still another object of the present invention is to provide a plasticarticle such as a cutlery item, molded from a light transmittingthermoplastic material, which is metallized on one side only. In thisrespect, it is worth mentioning that plated metal silverware isgenerally plated on both sides of the metallic substrate—display side aswell as underside. One of the unexpected aspects and novelty of thepresent invention is that the disposable plastic cutlery articles havingthe appearance of real silverware can be obtained in a commerciallyviable and economically attractive fashion by metallizing—on one sideonly. In other words, a clear or light-transmitting plastic cutleryarticle can be metallized on one side only with practically the sameresults and/or appearance as a cutlery article coated on both sides.

Still another object of the present invention is to provide a plasticcutlery article that emulates the reflective appearance of permanentflatware without being coated throughout and/or on all sides.

A further object of the present invention is to provide cutlery itemshaving a surface geometry that cooperates with the metallic coating.Cutlery items according to this aspect of the invention arecharacterized by having a plurality of surface design features includingalternating concave and convex areas, ribs, flutes, ornate patterns andother artistic features that enhance the reflective appearance andcommercial appeal of the metallized plastic cutlery.

A further object of the invention is to provide metallized cutleryarticles with design features or areas that have contrasting reflectiveproperties in comparison to the rest of the article, and thereforebecome sharply defined and visibly distinct and further add to thecommercial appeal of the metallized articles. For instance, the surfaceof the plastic article may include alternating smooth and texturedareas, or alternating engraved and non-engraved areas, or patternsthereof that, upon metallization, are adapted to standout and highlightthe reflective contrast between the smooth and textured areas or betweenthe engraved and non-engraved areas of the plastic article.

An additional object of the present invention is to provide a method forimproving the adhesion between the metallic coating layer and theplastic substrate by subjecting the metallized plastic cutlery items toa post-metallizing curing step.

Another object of the present invention is to provide a method forimproving the adhesion between the metallic coating layer and theplastic substrate by pre-treating the plastic cutlery article withtreatments such as flame treatment, plasma treatment or subjecting it toa corona discharge.

Still another object of the present invention is to provide metallizedplastic cutlery items, with improved abrasion resistance and adhesionbetween the plastic article and the metallic coating layer, by applyinga clear coating over the thin metallic coating layer. The clear coatingor overcoat enhances the abrasion resistance characteristics of themetallic layer and can be applied by spraying or other means. FDAapproved versions of over coating compositions can be readily obtainedfrom a variety of vendors.

A further object of the present invention is to provide metallizedcutlery, with improved abrasion resistance and adhesion between theplastic article and the metallic coating layer, by applying a clearsilicon dioxide plasma coating over the thin metallic coating layer.

Yet another object of the present invention is to provide metallizedcutlery items having good opacity and enhanced optical density byincorporating a color tint, such as a gray tint, in the base plasticresin material.

An object of the invention is a metallized plastic food service item,comprising a plastic tableware article with a thin metallic coatingdeposited on the plastic tableware item, wherein the thin metalliccoating is deposited by a vacuum deposition process. The tableware itemsinclude cutlery such as forks, spoons, knives, as well as othertableware items such as trays, plates, bowls, and cups.

Yet a further object of the invention is a metallized plastic foodservice item, wherein the thin metallic coating is selected of a metalfrom the group consisting of silver, steel, stainless steel, chromium,aluminum, copper and gold. For commercial reasons, the thin metalliccoating is generally less than 3000 nanometers (nm) and in oneembodiment of the invention is less than 1000 nm. In a furtherembodiment of the invention the thin metallic coating is less than 200nm. In addition, the article can further comprise a thin overcoat of acurable clear coating on the thin metallic coating. In addition, theplastic tableware article can have the metallic coating disposed on asingle surface of the plastic tableware article.

An additional object of the invention is a metallized plastic foodservice item, wherein the plastic tableware article is composed ofpolystyrene or other light transmitting plastic material and is producedby injection molding; and, wherein the metallized plastic food serviceitem has an optical density of less than 5.5 and preferably less than2.0 as measured by a densitometer. Optical density should be greaterthan about 0.5 as the aesthetic appearance at lower values is not highlypleasing.

An object of the invention is a metallized plastic food service articleproduced by the process comprising the steps of forming a plastic bodyby injection molding, placing the plastic body into a vacuum metallizingunit, and depositing on the plastic body a thin metallic coating by avacuum deposition process. In one embodiment the vacuum depositionprocess is physical vapor deposition, and in particular sputtering vapordeposition, with the sputtering deposition process utilizing plasmagenerated by Argon or mixtures of Argon and Nitrogen.

A further object of the invention is to enhance the adhesion andabrasion resistance of the metallic coating by holding the metallizedarticles in a clean and dry area and subjecting them to spontaneouscuring for a period ranging from about one day to about two weeks.

Still other objects and advantages of the present invention will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein we have shown and described only a fewembodiments of the invention, simply by way of illustration of certainmodes contemplated by us for carrying out our invention. As will berealized, the invention is capable of a variety of differentembodiments, and its several details are capable of modifications invarious respects, all without departing from the spirit and the scope ofthe invention.

The features and advantages described herein are not all-inclusive and,in particular, many additional features and advantages will be apparentto one of ordinary skill in the art in view of the drawings,specification, and claims. Moreover, it should be noted that thelanguage used in the specification has been principally selected forreadability and instructional purposes, and not to limit the scope ofthe inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings,wherein like reference numerals designate like structural elements, andin which:

FIG. 1A shows an isometric view of a fork with metallic coating that hasbeen constructed in accordance with an embodiment of the invention.

FIG. 1B is a side profile view of a fork with metallic coating inaccordance with an embodiment of the invention.

FIG. 2A is an isometric view of a spoon with metallic coating inaccordance with an embodiment of the invention.

FIG. 2B is a side profile view of a spoon with metallic coating inaccordance with an embodiment of the invention.

FIG. 3A is an isometric view of a knife with metallic coating inaccordance with an embodiment of the invention.

FIG. 3B is a side profile view of a knife with metallic coating inaccordance with an embodiment of the invention.

FIG. 4 is a cross-sectional view of a typical cutlery item exhibiting ametallic coating in accordance with an embodiment of the invention.

FIG. 5 is an isometric view of a knife with metallic coating depositedon a portion thereof in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

One intention of the instant invention, inter alia, was to developdisposable cutlery articles that emulate permanent flatware or metalsilverware. The present invention recognizes that—imparting a metallicappearance to disposable plastic cutlery would enhance the perceivedvalue and quality of the cutlery items and bridge the perception gapbetween plastic cutlery and permanent flatware. Prior to the instantinvention there were two main classes of flatware or cutlery—(I)Permanent Flatware or Silverware, characterized by its durability,metallic appearance and upscale image; and, (2) Plastic Cutlery knownfor its convenience and disposable characteristics but generallyregarded as a low-end alternative to permanent flatware and not asaesthetically attractive. The instant invention provides a new categoryof plastic flatware articles that retain their disposable character yetoffer the upscale image, reflective appearance and elegance comparableto their more expensive silverware counterparts.

Historically, “silverware” has been around for centuries, while“stainless steel cutlery” was developed and patented around 1916 and hasbeen around commercially since around the 1920s. The development ofstainless steel cutlery is generally attributed to Harry Brearley ofSheffield, England (U.S. Pat. No. 1,197,256 titled “Cutlery”, Sep. 5,1916). Plastic cutlery has been around at least since 1960s. This iscorroborated by the filing dates and subject matter in U.S. Pat. No.3,136,416. Specifically, in Column 1, lines 8-11 of U.S. Pat. No.3,136,416 to Goldrosen filed on Nov. 22, 1961, particular reference ismade to molded forks, knives and spoons.

Despite the facts that—plastic cutlery has been available for at least40 years; stainless steel cutlery has been around for over 80 years;silver-plated metal flatware was available for several centuries; andmetallizing methods have also been known in the art—there was no plasticcutlery product that emulated permanent flatware or metal silverwareprior to the instant invention.

The term “silverware” refers to flatware or cutlery articles that areeither made of silver or made of a metallic materials and then silverplated. The term is sometimes also used generically for metal orstainless steel flatware. The Encyclopedia Britannica defines“silverware” as “table knives, forks and spoons that are made ofsilver”; while Dictionary.com defines silverware as “(1) Hollowware andflatware made of or plated with silver; and (2) Metal eating or servingutensils”. Thus, for all purposes “silverware” connotes either silverflatware; or silver-plated flatware; or just generically metal flatwareor cutlery, which may be silver in appearance or any other metallicappearance.

The terms such as cutlery, flatware, serving cutlery, cutlery items,cutlery articles, utensils, eating implements, food implements, foodservice tools, or food-handling implements as used in this descriptionand claims are used in a generic and broad sense. These terms encompassdisposable plastic cutlery items molded into standard food-handling orserving implements such as forks, spoons, knives, serving utensilsand/or combinations thereof including spatulas, sporks, ladles, seafoodforks, seafood picks, soup spoons, and the like. Accompanying items suchas napkin rings, candle holders, and centerpiece receptacles aresometimes designed to match the cutlery items. Finally, the variousassortments of goblets, glasses, soup bowls, dishes, plates, trays,champagne flutes, lids, and the like are also sometimes matched to therest of the serving items and are all within the scope of the presentinvention wherein all these articles are considered tableware. Theembodiments are merely illustrations of the techniques, and there aremany other variations and applications all within the scope of theinvention.

In contrast to metal flatware which exhibits the color of the materialof construction or the subsequent plating treatment imparted to thearticle, plastic flatware or cutlery is generally available in either“natural, clear or non-colored” or “colored” forms or versions.Disposable cutlery items, which are currently sold in the marketplace,are typically constructed of either polystyrene and/or polypropyleneresins. Most commercial plastic cutlery which is “natural, clear ornon-colored” is made of clear polystyrene resin and exhibits thetransparent characteristics of the material of construction namelypolystyrene. “Colored” plastic cutlery can be made of either polystyreneor polypropylene and is generally colored by using a “color concentrate”that is added to the base resin in an injection molding process.

In light of the above disclosure and utility of metallizing plasticcutlery articles with the purpose of simulating metal flatware—it wouldbe apparently desirable, for a person of ordinary skill, to metallize orcoat plastic cutlery articles throughout, in other words on all sidesand surfaces of the article. All cutlery articles heretofore have beencompletely coated on all sides. This typical approach of coating theentire article would lead a person of ordinary skill towards either,electroplating type processes wherein the entire article can besubmerged in a plating solution; or, other metallizing processes wherecutlery articles are subjected to the metallizing source at leasttwice—firstly to coat the display side (face side) and, secondly to coatthe underside or undersurface of the cutlery articles. It would bereadily recognized that both of the approaches for practicing theinvention of metallizing cutlery articles, namely by coating thearticles in a plating bath or subjecting them to metallizing twice havedisadvantages that make them neither practical nor economical.Furthermore, plating has other disadvantages which have been discussedherein.

The inventors overcame the problem of preserving the economics ofmetallizing plastic cutlery articles without resorting to a platingprocess or to a two stage metallizing method. One of the unexpected andnovel aspects of the present invention is that the disposable plasticcutlery articles having the appearance of metal silverware or permanentflatware can be obtained in a commercially viable and economicallyattractive fashion by molding plastic cutlery articles from clear orlight-transmitting resins and metallizing them on one side only. Inother words, a clear or light-transmitting plastic cutlery article canbe metallized on one side only with practically the same results and/orappearance as a cutlery article coated on both sides.

In a further embodiment of the invention, currently being practicedcommercially, the plastic cutlery articles are vacuum metallized on oneside only and yet achieve the desired appearance and result of emulatinga metal silverware or permanent flatware article. It is worth notingthat permanent flatware is either plated on both sides or the entirearticle is constructed from the same bulk material throughout, wherebytypical flatware articles generally exhibit similar appearance on allsides thereof. The plastic cutlery article according to a thirdembodiment is molded from crystal polystyrene resin and is vacuummetallized on one side only.

Also, it should be readily apparent that metallizing or depositing themetal layer on only one side of the article offers several economicadvantages in comparison to coating the entire article. Firstly, thereare coating or metal material savings, as approximately only one-half ofthe surface area of the parts is metallized. Secondly, there aremetallizing process savings as parts are subjected to the depositionmechanism only once, and only one pass through the metallizer ormetallizing equipment is required. Thirdly, there are output orproductivity gains resulting from shorter cycle times as the samemetallizing equipment or asset can coat or metallize twice as many partswith only one sided coating as would be possible for metallized partsrequiring coating on both sides thereof. Lastly, one sided coatingsimplifies part handling as no turning or flipping of the parts formetallizing the underside or second side is required.

Thus, while the metallized cutlery can be coated on both sides, coatingthe cutlery articles on both sides is more expensive and economicallyless attractive, as two metallizing cycles would be required to coatboth sides of the articles resulting in reduced output per unit time;the metal material cost would be increased; the capital outlay wouldalso increase, as in order to sustain an equivalent output rateadditional metallizing machines would be required; lastly, coating bothsides would require more complex part handling mechanisms for turning orflipping the parts for presenting the second side of the articles formetallizing, without affecting or scratching the metallic coating on theside previously metallized. Thus, the economic benefits of coating ormetallizing on one side only, enhance the commercial viability of thisembodiment of the invention and the ability to practice the invention ina competitive manner and offer metallized plastic cutlery at reasonableprices for disposable applications.

From an aesthetic standpoint the metallized coating is applied to theside which typically faces up in a traditional table-setting for placingcutlery implements. A traditional place setting typically includes afork with tine facing upwards, a spoon with the concave bowl facingupwards and a knife with the serrated edge placed pointing left and awayfrom the user; handle portions of all eating implements are towards theuser. Various other tableware articles may accompany the traditionalsetting.

It would be clear to those skilled in the art that a variety ofthermoplastic polymer types and/or resin grades can be employed for thepurpose of making the cutlery items of the present invention. Materialchoices for such applications are governed by a variety of factorsincluding consumer preferences, cost, engineering requirements,availability and other economic and market factors. The primaryselection criteria for a base plastic material or resin include (1)mechanical and thermal functionality with respect to strength, rigidity,and use temperature; (2) acceptable melt viscosity and flow propertiesfor injection molding into desired shapes with high surface gloss; (3)ability to withstand the metallizing process and offering reasonablyhigh surface energy to effect good adhesion between the plastic resinand the applied metal layer; (4) reasonable cost for disposable use; and(5) good optical and surface gloss properties.

According to an embodiment of the invention, wherein the cutleryarticles are coated on one side only, the light transmissioncharacteristics or transparency of the material are also important forobtaining metallized cutlery articles that emulate metal flatware, andoffer the appearance of being coated on both sides (the metallized sideas well as the opposing side) yet are coated on one side only.

Several thermoplastic resins having the desired optical and functionalcharacteristics including polystyrene (PS), polymethyl methacrylate(PMMA), acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile(SAN) and polycarbonate (PC) can be employed for achieving the objectsof this invention. Polystyrene (PS) was the material of choice for someembodiments of the invention. Polystyrene resin has a lower costcompared to ABS, PC and SAN. It is the general experience of thoseskilled in the art that polystyrene cutlery is perceived as the higherend disposable cutlery in the marketplace. One criterion for selectingcrystal polystyrene for this application is the relatively high flexuralmodulus of polystyrene compared to other resin materials in anequivalent price range. More specifically, the flexural modulus ofpolystyrene is superior to that of polypropylene. Crystal polystyrenehas excellent light transmission characteristics due to its amorphouspolymeric structure as opposed to polypropylene, which is highlycrystalline in nature. In addition, variable cooling rates such as areencountered in the injection molding process have little effect on thelight transmission characteristics of the molded article due to theamorphous polymeric structure of polystyrene. In other words, crystalpolystyrene has a large processing window with respect to its opticalcharacteristics. In addition, polystyrene exhibits a higher surfaceenergy compared to polypropylene and other polyolefins and, therefore,offers better metal-to-substrate adhesion compared to polyolefin resins.

Thus, in one embodiment of the present invention, the cutlery items aremolded from a suitable crystal polystyrene resin grade having goodclarity; physical properties; and, desirable flow, melt viscosity andmolding characteristics from a production and manufacturing standpoint.Processing aids that are routinely added to commercial resins such asmineral oil and surface waxes are exuded to the surface of the part andinterfere with obtaining adequate adhesion between the deposited metaland the part surface. Therefore, in order to ensure that durable metalcoatings are deposited on the surface of the cutlery article, the resinused must be of high quality and primarily free of mineral oil and othervolatiles.

It will be recognized by those skilled in the art that the reflectiveappearance of a metallized plastic article would, inter alia, beinfluenced by the surface characteristics of the unmetallized plasticarticle; the metal coating itself, the tint coloration of the article,and the thickness of the metal coating. Coatings deposited by vacuum orvapor deposition are sufficiently thin to replicate the surface of thesubstrate. Therefore, metallic coatings deposited on smooth and polishedsurfaces will have higher reflectance compared to metallic coatingsdeposited on rough and unpolished surfaces.

Also, it is generally recognized that extremely thin coatings aregenerally not as reflective as thicker coatings. The non-reflectiveaspect of such thin coatings is utilized in food containers formicrowave heating and browning of certain foods, wherein reflectivecharacteristics for such articles would cause harmful effects such assparking when subjected to microwave energy.

In addition, it is well known that certain metals are more reflectivethan others at comparable coating thickness. Accordingly, in one of theembodiments of the invention plastic cutlery articles are molded using apolished mold surface to obtain a smooth part surface finish aftermolding. The smooth surface or finish on the articles allows depositionof smooth and reflective metal coatings. It will be appreciated that inorder to emulate the appearance of a metal silverware article the metalcoating should resemble the metal silverware; and, the surface of theplastic cutlery article is sufficiently smooth to allow for depositionof a smooth metallic film. In one embodiment of the invention a plasticarticle is subjected to vacuum deposition and metallized with a thincoating of stainless steel that is at least 30 nanometers in thicknessand typically more than 60 nanometers in thickness, yet have anaesthetically pleasing reflective appearance.

It is well known in the art to provide an ornate pattern or design onthe surface of a plastic part by engraving. According to anotherembodiment of the invention the cutlery articles can be furtheraccentuated by providing alternating smooth and engraved surfaces duringmolding whereby the variations in surface finish on the part effectvariations in reflectance after metallization of the cutlery articlesand the reflective coating highlights the molded-in design.

Referring now to FIGS. 1A, 1B, 2A, 2B, 3A and 3B there are shown typicalcutlery items, which have been constructed in accordance with thepresent invention wherein like parts are designated by like referencenumerals.

FIG. 1A shows an isometric perspective view of a fork represented byreference numeral 10 having its general construction in accordance withthe present invention. Fork 10 has a tines portion 11 and a handleportion 12. Fork 10 also contains surface features in the form of flutesor other geometrical artistic contours generally denoted by referencenumeral 13. A surface-coating layer of metal is deposited on at leastone of the surfaces of the plastic fork to impart the appearance of ametallic cutlery piece. In another embodiment of the invention themetallic coating is applied to the display side or the side that isfacing-up in a typical place setting presentation for a food-event. Themetallic coating on the plastic surface of the fork is denoted byreference numeral 14.

FIG. 1B shows a side view of Fork 10 wherein the various fork portionsare identified with the corresponding reference numeral designations ofFIG. 1A. The metallic coating is imparted on only the upper face ordisplay surface of the plastic fork and is represented by referencenumeral 14.

Referring now to FIG. 2A, there is shown an isometric perspective viewof a spoon represented by reference numeral 20 having its generalconstruction in accordance with the present invention. Similarly, FIG.2B shows a side view of spoon 20 wherein like reference numeralsrepresent like parts or features. Spoon 20 has a bowl portion 21 and ahandle portion 22. Spoon 20 also contains surface features in the formof flutes or other geometrical artistic contours generally denoted byreference numeral 23. A surface-coating layer of metal is deposited onat least one of the surfaces of the plastic spoon to impart theappearance of a metallic cutlery piece. In a further embodiment of theinvention the metallic coating is applied to the display side or theside that is facing-up in a typical place setting for a food-event. Themetallic coating on the plastic surface of the spoon is denoted byreference numeral 24.

FIGS. 3A and 3B respectively show isometric and side views of a kniferepresented by reference numeral 30 having its general construction inaccordance with the present invention. Knife 30 has a blade portion 31and a handle portion 32. Knife 30 also contains surface features in theform of flutes or other artistic contours generally denoted by referencenumeral 33. A surface-coating layer of metal is deposited on at leastone of the surfaces of the plastic knife to impart the appearance of ametallic cutlery piece. In yet another embodiment of the invention themetallic coating is applied to only one of the sides of the knife. Themetallic coating on the plastic surface of the knife is denoted byreference numeral 34.

Referring now to FIG. 4 there is shown a rear cross-section of a typicalcutlery item 40. The stem portion of the cutlery item 40 is denoted byreference numeral 42. In the described embodiment the stem 42 hasvarious curved and flute-like features on its surface denoted byreference numeral 43. The cutlery item has a metallic coating applied onone of its surfaces shown in the cross-sectional view by referencenumeral 44. The metallic coating 44 is very thin in relation to the bulkof the article (not shown to scale) and follows the contours on thesurface of the part. The thickness of the metallic coating can varydepending upon the particular application and in certain embodiments isless than 3,000 nanometers. In further embodiments of the invention thethickness of the metallic coating is less than 1,000 nanometers. Itwould be readily apparent to those skilled in the art that due to themetal weight, cost, and coating time considerations, a thin metalliclayer is commercially desirable. For example, in one embodiment of theinvention, the thickness of the metallic coating is less than about 200nanometers. The thickness of the metal depends upon the properties ofthe plastic and the metal, with the overall objective of achieving asatisfactory metal-like appearance.

The cutlery items in FIG. 1A through FIG. 3A have been shown as havingparticular configurations and specific design feature ratios, e.g.fork-tine length to overall fork length, spoon bowl length to overallspoon length, and knife blade length to overall knife length. It will bereadily understood by those skilled in the art that these cutlery itemsare manufactured and marketed in a variety of geometricalconfigurations, feature ratios and sizes. The physical configurationsand design features and aspect ratios exhibited here are done for thepurpose of illustration and not by way of limitation. Furthermore,various patterns and ornamental features as are known in the art canadorn the stem, and the present invention is applicable to any suchdesigns.

Referring now to FIG. 5, there is shown an isometric perspective view ofa knife represented by reference numeral 50 having its generalconstruction in accordance with an exemplary embodiment of the presentinvention. Knife 50 has a first portion 50A and a second portion 50B.According to this embodiment the first portion 50A of the knife 50 ismetallized while the second portion 50B retains its as-moldedappearance. The first and second portions of the knife 50 may be furtheradapted to have different physical characteristics. Alternatively, thefirst and second portions may be adapted to coincide with distinctphysical or functional sections of the article. As shown in FIG. 5,first portion 50A is adapted to be the blade portion 51, and secondportion 50B is adapted to be the handle portion 52 of knife 50. It willbe recognized by those of ordinary skill that the first and secondportions, shown herein, are exemplary divisions of the article and willnot always necessarily refer to or coincide with specific physical,geometrical, or functional features of an article. The blade portion 51contains a plurality of serrations 53. The handle portion 52 contains aplurality of surface features or patterns generically denoted byreference numeral 53. A surface-coating layer of metal is deposited onat least one of the surfaces of the blade portion 51 to impart theappearance of a metallic cutlery piece. The metallic coating on theblade portion 51 of the plastic surface of the knife is denoted byreference numeral 55. The handle portion 52 of knife 50 is not coatedwith a metallic layer and retains the basic initial appearance of theplastic surface. Thus, the blade portion 51 displays a metallicappearance while handle portion displays a non-metallic appearance.

According to a variant of the embodiment of the invention, shown in FIG.5, the metallic coating 55 is applied to only the display side of theknife and wherein the blade portion 51 is constructed from a lighttransmitting plastic resin while the handle portion 52 is constructedfrom a colored plastic resin.

Metal coating on the cutlery items can be applied by any of the knownvacuum deposition procedures or techniques. Vacuum metallization ordeposition is the deposition of a film or coating in a vacuum orlow-pressure plasma environment. The term plasma generally refers to anion- or electron—rich gaseous environment for providing appreciableelectrical conductivity. Vacuum deposition is a term that is applied toprocesses that deposit atoms or molecules one at a time, such as inphysical vapor deposition (PVD) or low-pressure chemical vapordeposition (LPCVD).

Typical PVD techniques can be used for accomplishing the objectives ofthe current invention. In Physical vapor deposition or (PVD) processesmetallic particles are vaporized from a solid or liquid source andtransported as vapor through vacuum or low-pressure gaseous or plasmaenvironment. The vaporized material can be an element, alloy orcompound. The condensation of the particles produces a thin-metalliccoating or film on the substrate surface and imparts a metallic look tothe substrate. Various variants of the PVD processes have been describedin the art, including Vacuum Evaporation, Sputter Deposition orSputtering, Arc Vapor Deposition and Ion Plating. Additional Evaporationtechniques include Filament Evaporation, Flash Evaporation, andElectron-beam Evaporation.

Deposited film or coating thickness typically obtained by PVD processesranges from few nanometers to thousands of nanometers. PVD processes canbe used to form thick deposits through multilayer coatings that can beimparted in a series of steps. Very thick coatings are generally notcommercially desirable due to higher costs associated with increasingamounts of coating material needed for thick coatings, and longerprocessing times required for deposition thereof. Furthermore, extendeddeposition times may cause over heating and thermal distortion of theplastic article being coated. As would be realized by those of ordinaryskill, metal coating thickness deposited on a commercial article becomesa practical and economic decision as long as the aesthetic appearance issatisfied. According to an embodiment of the present invention, themetallic coating on the surface of the articles is generally less than3000 nanometers (nm) and in a further embodiment of the invention isless than 1000 nm. In yet another embodiment of the invention themetallic coating is less than 200 nm in thickness. And in yet an evenfurther embodiment, the metallic coating is at least 30 nm.

To summarize, according to some of the embodiment of the presentinvention: (1) the cutlery articles are made of a light-transmittinggrade of a thermoplastic resin material; (2) the thermoplastic resin issubstantially free of mineral oil and other volatile additives; (3) themetallic coating is applied by a physical vapor deposition (PVD)process; (4) the metallic coating is applied to only one side of thecutlery articles; (5) the metallic coating is of the same composition asthe stainless steel alloy used in permanent flatware; and (6) Themetallic coating thickness is less than 200 nanometers but greater thanabout 30 nm.

In one embodiment of the present invention the metallic coating isapplied to the plastic cutlery items molded from polystyrene bysputtering vacuum deposition process (also referred to as sputterdeposition or sputtering) on only the display side of the plasticcutlery items.

Sputtering or sputter deposition is a PVD coating process which isconducted in an evacuable coating or sputtering chamber. The source ofthe coating material, the target, is mounted opposite to the substrateitems in the sputtering chamber which is then evacuated to a basepressure which typically ranges from 10⁻⁵ to 10⁻¹⁰ Torr (1 Torr=1 mm Hg)depending upon the process or application. Thereafter, the evacuatedcoating chamber is backfilled with a continuous flow of an inert gassuch as Argon to a pressure of 1 to 100 mTorr (1 mTorr=0.001 Torr=0.001mm Hg) to create a gas plasma or glow discharge between the metal targetand the item or substrate to be coated. A negative DC or RF voltage isapplied to the metal sputtering target (metal source) in order toinitiate positive-ion bombardment. Positively charged gas ions,generated in the plasma region, are propelled at high velocities towardsthe target (negative potential), resulting in the ejection of atomicsize particles of the metal target (source material) that are directedtowards the substrate. Thus, Sputtering is a non-thermal vaporizationprocess where surface atoms are physically ejected from the metal sourceor target by momentum transfer or exchange from an energetic bombardingparticle or gaseous ion accelerated from the plasma. A particularadvantage of the sputtering technique is the ability for depositingmetals as well as metal alloys and is well suited for depositingstainless steel alloy compositions of the type typically employed formaking traditional metal cutlery.

Generally, the metallic coating deposited on the articles displays thecharacteristic color of the metal source. However, tints can beincorporated in the metal source or the base metal or by using anappropriate reactive gas during the deposition process for imparting atinted reflective appearance to the plastic articles.

In testing of one of the embodiments, commercial plastic cutlery piecesin the form of a fork, spoon and knife made from either polystyrene orpolypropylene were introduced into a lab-size sputtering chamber. Thesputtering equipment was provided by Soleras, Inc. A stainless steeltarget was mounted in the sputtering chamber. The particular compositionof stainless steel was 304. The chamber was then pumped down until avacuum was reached in the range around 10⁻³ mm Hg. Argon was supplied tothe chamber to generate the plasma. A negative voltage in the range of 5to 10 kW was applied to the cathode in the evacuated chamber. Thecoating operation at this setting was continued for about 1 to 5seconds. Following coating, the power was turned off and vacuum was thenreleased allowing the pressure in the chamber to rise to atmosphericpressure. Thereafter, the chamber was opened and parts were removed fromthe chamber and examined. Various tests were conducted on the plasticcutlery items for peel-off adhesion. In some trials, coating was appliedto both sides of a part. In other iterations it was applied to only oneside of the part.

It was found that polystyrene cutlery exhibits much better coatingadhesion compared to polypropylene cutlery. In this particular testexample—power setting of 7.5 kW and 3-second sputtering time were deemedto be the optimum conditions for good adhesion, surface appearance anduniformity of coating. The most remarkable finding from thisexperimental work was that the coating could be applied to just one sideof the clear polystyrene part to obtain the desired metallic look oreffect. This unexpected result reduces manufacturing time and thecomplexity of manufacturing while at the same time providing twice theutilization of the metal target. Thus, one sided coating was obtained bypresenting only the display side of the plastic article to the metalsource or target while the underside of the plastic article was facingaway from the metal source and was not directly presented to the metalsource. Coating on both sides would have required presenting both thedisplay side and the underside to the metal source and would haverequired two separate metallizing operations.

For a given hardware and power setting configuration, the metaldeposition or the thickness of the metal layer is proportional to theduration of sputtering. When a clear or transparent article is subjectedto sputter vapor deposition or sputtering for very short durations(typically less than 1 second) the resulting metal-layer is also verythin and merely imparts a hue to the article. The article as a result isnot very reflective and practically retains its light-transmittingcharacter. An increase in the duration of sputtering (sputter time)results in a corresponding increase in the metal-layer thickness and thereflectance of the article and a corresponding reduction in thelight-transmission.

A useful tool for monitoring the thickness of the metal layer applied toa clear article is an optical densitometer which measures opticaldensity of the article.

Optical density is represented by the following equation:OD=log₁₀(1/T)  (1)Where OD is optical density, and T is TransmittanceTransmittance, T is defined by the following equation:T=I/I _(o)  (2)Where, I is the intensity of transmitted light, andI_(o) is intensity of incident light.

Thus, for a completely transparent material or article, the opticaldensity is 0 (log₁₀1=0), since transmittance (the ratio of theintensities of transmitted light to incident light) is 1. It would beappreciated by those skilled in the art that increasing the amount ofcoating or deposition time would result in a corresponding reduction inthe intensity of transmitted light and therefore a correspondingreduction in transmittance and an increase in optical density. However,after a certain point, increasing the amount of deposited metal willonly bring marginal improvements in optical density due to thelogarithmic relationship between optical density and transmittance. Foran article having a transmittance of 0.1 or transmitting 10% of incidentlight the optical density is 1.0 (log₁₀=10=1). For an article having atransmittance of 0.01 or transmitting 1% of incident light the opticaldensity is 2.0 (log₁₀100=2). Similarly, for an article having atransmittance of 0.001 or transmitting 0.1% of incident light theoptical density is 3.0 (log₁₀1000=3).

Typical cutlery articles molded from clear polystyrene resin accordingto an embodiment of the current invention have an “initial opticaldensity” of between 0 and 0.3. The term “initial optical density” asused herein refers to the “optical density prior to metallization”. Onceagain, optical density for the clear articles is dependent on the natureof the molded surface, the thickness of the plastic article and thepresence of any surface features on the article. As these clear articlesare vacuum-metallized, they exhibit increasing optical densities inproportion to the duration of metallizing and/or the thickness of themetallic coating. At optical density values of less than about 0.5, theoverall appearance of the articles is generally considered unacceptabledue to the lack of sufficient aesthetic appeal and poor reflectivity. Atoptical density values above 0.5, the articles have a fair degree ofreflectivity and deemed suitable for certain events.

As the optical density of the article is increased from 0.5 to 0.8, ageneral increase in reflectance is observed, although the metal layerstill tends to be very thin. As optical density of the article inincreased above 0.8 the articles begins to exhibit sufficient opacityand a more attractive metallic appearance. At about the 1.5 opticaldensity level, the metallized parts have sufficient opacity orreflective properties and are generally considered acceptable accordingto an embodiment of the invention. In another embodiment of theinvention the optical density of the metallized parts is below 2.0. Instill another embodiment of the invention the optical density of themetallized parts is below 3.0. As should be readily apparent, anincrease in optical density can be readily attained by increased metaldeposition or longer sputter time. It will be appreciated by those ofordinary skill that the optimal metal layer thickness or optical densityis reached when the article has acquired an attractive reflectiveappearance and opacity for commercial acceptance. Once this optimalstate is reached enhancing optical density or increasing metal thicknessbeyond the optimal state will not be economically beneficial. Once againthe determination of appropriate optical density (or metal thickness)versus appearance is influenced by economics, with a minimum opticaldensity being about 0.5 on the lower end. Although optical densityvalues of about 5.5 are obtainable with vacuum metallizing processes onclear parts, optical density values of above 1.5 are typically deemedacceptable for the purpose of metallized plastic cutlery.

A further method for enhancing optical density without increasingsputter time or metal thickness is to incorporate a light transmittingdye or tint in the base material or resin. Typically grayish tints workwell but tints in a variety of colors can be utilized for enhancing theopacity of the cutlery item and imparting other appearance effects.Since the tint itself provides some degree of opacity the thickness ofthe metallic coating layer thickness can be proportionally reduced toimprove the economics of the process. For instance, a clear plasticcutlery article may have an initial optical density (prior tometallization) of 0-0.2; however, the addition of a tint in the baseresin can readily increase the initial optical density of the cutleryarticle by about 0.1 to 0.5, in other words the range of initial opticaldensity of the tinted cutlery article would become 0.1 to 0.7, thereforethe amount of metal required to achieve a final desired optical densitywould be commensurately reduced. According to an embodiment of theinvention plastic cutlery having adequate reflective characteristics isproduced by incorporating color tints in the base resin and depositingan extremely thin metal layer having a thickness of between 30 nm to 60nm.

According to another embodiment of the invention the plastic article ismolded from a plastic resin with two distinct portions—a first portionand a second portion; and, wherein the first portion is rendered clearor is tinted by using a light transmitting tint added to the plasticresin, and the second portion is colored with an opaque colorantincorporated into said plastic resin, and wherein only the first portionof the plastic article is metallized by a thin metallic coating.

Contact by the metallized cutlery with various foods could affect thecoating or cause peel-off, therefore the metallized cutlery wassubjected to confirmatory tests in a variety of food environments. Testsincluded subjecting metallized cutlery to boiling water, boiling tomatosauce, boiling water-vinegar mixture, lemon juice, coffee, ice, thermalcycles with alternate exposure to boiling water and ice-cold water, andshipping bulk cutlery across the country. It must be noted that thecoated cutlery is susceptible to scratches due to abrasion as anyordinary metal cutlery.

It would be appreciated by those skilled in the art that a prerequisitefor practical use and commercial acceptance of metallized plasticcutlery is that the metallic coating layer should exhibit sufficientadhesion to the plastic material and reasonable abrasion resistance forutilization as a food implement. Tape peel tests are normally used fortesting the adhesion between the cutlery item surface and the metallayer deposited thereon. Adhesion is also related to abrasion resistanceor durability of the coating. Adhesion and abrasion resistance of thedeposited metal layer to the substrate surface can be enhanced by avariety of methods.

As indicated earlier, the adhesion between the plastic substrate or theplastic article and the deposited metal layer can be enhanced byutilizing a volatiles free resin completely free of mineral oil andother lubricants. Another way to improve adhesion and abrasionresistance of the metallic coating it to pre-treat the surface of theplastic part by either flame treatment, plasma treatment or coronatreatment for increasing the surface energy of the cutlery item. Surfacetreatments for enhancing the surface energy of plastic parts are wellknown in the art. For example, a typical corona treatment can enhancethe surface energy of a polystyrene part from 35 dynes to about 46dynes.

Yet another method for improving abrasion resistance or durability ofthe metallic coating is to apply a light transmitting heat- orUV-curable coating, which serves to seal-off the deposited metal layer.Such coating compositions are well known in the art and are used toprovide a barrier overcoat over a variety of articles including Compactdisks and DVDs. FDA approved compositions of hardenable clear coatings,which can be applied by spraying, are also readily available forcovering food service articles.

Further improvement in coating strength can be achieved by subjecting avacuum metallized cutlery article to a secondary Chemical VaporDeposition (CVD) process for depositing a thin over coating of asubstantially clear and abrasion resistant material. For exampleplasma-enhanced CVD (PECVD) process can be used to deposit thin films ofSilicon dioxide or other clear materials.

Another technique for improving adhesion of the metallic coating to thearticle is by utilizing a mixture of Argon and Nitrogen for plasmageneration in the sputtering chamber during metal deposition. Thetypical concentration of Nitrogen in the Nitrogen and Argon mixture isbetween 10% and 40%. Sputter deposition conducted with a mixture ofNitrogen and Argon yields a metal layer with enhanced durabilitycompared to Argon plasma alone.

The inventors have discovered that subjecting the metallized plasticcutlery articles to a curing process after metallizing, results in aspontaneous improvement of metal to plastic adhesion as well as theabrasion resistance of the metallic coating. The curing can beaccomplished by simply storing the metallized articles in a clean anddry area. The spontaneous improvement in plastic to metal layer adhesionand abrasion characteristics of the metallic layer continues for severaldays after the parts are vacuum metallized. It is preferable that duringthe curing process the parts are stored under relatively dry orlow-humidity conditions. Appreciable improvement in the adhesion andabrasion characteristics of the metal layer to the plastic article istypically seen within 24 to 72 hours of curing at room temperature aftermetallizing. In an embodiment of the invention the metallized articlesare stored for a period of about 2 weeks prior to commissioning them foruse or sale. The term curing period, storing period, holding period,post-metallizing holding period have been used here to connote that theplastic articles are held in a quiescent or undisturbed state aftermetallizing.

It is also seen that the rate of curing can be accelerated by subjectingthe parts to a higher temperature and relatively low humidityenvironment. Thus, if the parts are heated during the curing or holdingperiod the rate of improvement in both adhesion and abrasioncharacteristics is faster.

A useful method of manufacture of metallized plastic cutlery and othertableware according to the present invention is as follows:

Step 1: Molding plastic cutlery using traditional injection moldingtechniques.

Step 2: Taking out the plastic cutlery from the mold using a parttake-out device such as a side-entry or top-entry robot.

Step 3: Placing the individual pieces of cutlery in a non-contiguousmanner on transferring or conveying means wherefrom cutlery parts aretransferred to a vacuum depositing station. Cutlery pieces aremaintained in an individualized or non-contiguous manner to preventsurface masking by adjacent cutlery pieces during metallizing orcoating.

Step 4: Subjecting plastic cutlery to a vacuum deposition process.

Step 5: Collecting plastic cutlery that has been metallized andsubjecting it to a curing process for enhancing packing them intosuitable packaging containers for shipping.

Step 6: Holding the packaged container in a clean and dry area for apredetermined post-metallizing holding period prior to committingmetallized plastic cutlery for use or sale.

The predetermined post-metallizing holding period in step 6 can be aslong as 45 days. In one embodiment of the invention the holding periodis about 2 weeks. Step 6 can be conducted either at room temperature, orat a single elevated temperature, or at plurality of temperatures duringthe curing period. In one embodiment of the invention the curing formetallized articles is conducted at room temperature for about twoweeks. According to another embodiment of the invention the metallizedarticles are subjected to curing at a temperature of up to 150 degreesFahrenheit for about 1 to 3 hours.

Although, this invention has been described particularly in relation tometallizing plastic cutlery, it will be recognized that it is applicableto general food service items, tableware and other industries wherein itis desired to impart metallic coating onto plastic and non-plasticparts. Also, it would be realized by those skilled in the art thatvarious modifications, alterations and adaptations can be made to thisinvention without departing from the spirit and scope of this invention.

Numerous characteristics and advantages have been set forth in theforegoing description, together with details of structures and functionsof the present invention, and some of the novel features thereof arepointed out in appended claims. The disclosure, however, is illustrativeonly, and change may be made in arrangement and details, within theprinciple of the invention, to the full extent indicated by the broadgeneral meaning of the terms in which the appended claims are expressed.

The foregoing description of the embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed. Many modifications and variations are possible in light ofthis disclosure. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto.

1. A metallized plastic food service item, comprising: a plastictableware article molded from a light transmitting resin with at least afirst side and a second side; a thin metallic coating deposited on saidplastic tableware article by a vacuum deposition process, said thinmetallic coating is deposited by presenting just the first side of saidplastic tableware article to a metal source in said vacuum depositionprocess; and said thin metallic coating is of a sufficient thickness toimpart a reflective appearance to said plastic tableware article.
 2. Themetallized plastic food service item according to claim 1, wherein saidfirst side of said plastic tableware article is adapted for beingdisplayed in a table setting presentation.
 3. The metallized plasticfood service item according to claim 1, wherein said second side of saidplastic tableware article is adapted for being displayed in a tablesetting presentation.
 4. The metallized plastic food service itemaccording to claim 1, further comprising a tint in said lighttransmitting resin.
 5. The metallized plastic food service itemaccording to claim 4, wherein said tint is light transmitting andincreases an initial optical density of said plastic tableware articleby about 0.1 to 0.5.
 6. The metallized plastic food service itemaccording to claim 1, wherein said thin metallic coating is selectedfrom a group consisting of: silver, steel, stainless steel, chromium,aluminum, copper, gold, and compositions therewith.
 7. The metallizedplastic food service item according to claim 1, wherein said metalsource is selected from a group consisting of: silver, steel, stainlesssteel, copper, chromium, aluminum, gold and alloys thereof.
 8. Themetallized plastic food service item according to claim 1, wherein saidthin metallic coating includes a tint.
 9. The metallized plastic foodservice item according to claim 1, wherein said thin metallic coating isless than 3,000 nanometers in thickness.
 10. The metallized plastic foodservice item according to claim 1, wherein said thin metallic coating isless than 1000 nanometers in thickness.
 11. The metallized plastic foodservice item according to claim 1, wherein said thin metallic coating isless than 200 nanometers in thickness.
 12. The metallized plastic foodservice item according to claim 1, wherein said thin metallic coating ismore than 30 nanometers in thickness.
 13. The metallized plastic foodservice item according to claim 1, further comprising a clear coatingover said thin metallic coating for protecting said thin metalliccoating and enhancing the durability of said thin metallic coating. 14.The metallized plastic food service item according to claim 1, furthercomprising a thin protective overcoat of a clear coating over said thinmetallic coating, wherein said thin protective overcoat is deposited bya chemical vapor deposition process.
 15. The metallized plastic foodservice item according to claim 1, wherein said plastic tablewarearticle is an implement for handling and consuming food, selected from agroup consisting of: fork, knife and spoon.
 16. The metallized plasticfood service item according to claim 1, wherein said plastic tablewarearticle is selected from a group consisting of: tray, plate, cup andbowl.
 17. The metallized plastic food service item according to claim 1,wherein said plastic tableware article is at least partially composed ofpolystyrene.
 18. The metallized plastic food service item according toclaim 1, wherein said metallized plastic food service item has anoptical density of less than about
 6. 19. The metallized plastic foodservice item according to claim 1, wherein said metallized plastic foodservice item has an optical density of less than about
 3. 20. Themetallized plastic food service item according to claim 1, wherein saidmetallized plastic food service item has an optical density of greaterthan about 0.5.
 21. The metallized plastic food service item accordingto claim 1, wherein said plastic tableware article is produced byinjection molding.
 22. The metallized plastic food service itemaccording to claim 1, wherein said vacuum deposition process is asputtering deposition process.
 23. A method for making an aestheticallypleasing plastic food service product, comprising: molding a plastictableware article by the process of injection molding, wherein saidplastic tableware article has at least a first surface and a secondsurface; placing said plastic tableware article into a vacuummetallizing unit having a metal source with said first surface facingsaid metal source; depositing onto said first surface of the plastictableware article, a thin metallic coating, by a vacuum depositionprocess, of sufficient thickness to impart a reflective metal-likeappearance to the plastic tableware article; and subjecting said plastictableware article with said thin metallic coating for a predeterminedpost-metallizing holding period.
 24. The method according to claim 23,wherein said predetermined post-metallizing holding period isimplemented by heating said plastic food service product up to atemperature of about 150 degrees Fahrenheit.
 25. The method according toclaim 23, wherein said predetermined post-metallizing holding period isat least 24 hours and is implemented by storing said plastic foodservice product under clean and dry conditions.
 26. The method accordingto claim 23, wherein said predetermined post-metallizing holding periodis implemented by packing said plastic food service product in asuitable package, and storing said suitable package for a period ofabout two weeks.
 27. The method according to claim 23, furthercomprising spraying a clear coating and curing said clear coating. 28.The method according to claim 23, further comprising depositing a clearcoating by a vacuum deposition process.
 29. The method according toclaim 23, wherein said vacuum deposition process is a physical vapordeposition.
 30. The method according to claim 23, wherein said vacuumdeposition process is a sputtering vapor deposition.
 31. The methodaccording to claim 23, wherein said thin metallic coating is selectedfrom a metal chosen from the group of metals consisting of: silver,steel, stainless steel, chromium, aluminum, copper, gold andcompositions thereof.
 32. The method according to claim 23, wherein saidplastic tableware article is molded from a light transmitting plasticmaterial with a color tint.
 33. The method according to claim 23,wherein said thin metallic coating is less than 3000 nanometers inthickness.
 34. A metallized plastic food service item, comprising: aplastic tableware article comprising at least a first portion and asecond portion; a thin metallic coating deposited on only said firstportion of said plastic tableware article by a vacuum depositionprocess, said thin metallic coating is deposited by presenting only saidfirst portion of said plastic tableware article to a metal source insaid vacuum deposition process; said thin metallic coating is of asufficient thickness to impart a reflective appearance to at least saidfirst portion of said plastic tableware article; and wherein said firstportion of said plastic tableware article, having said thin metalliccoating, has an optical density of greater than about 0.5.
 35. Themetallized plastic food service item according to claim 34, wherein saidfirst portion is molded from a light transmitting plastic resin and saidsecond portion is molded from a colored plastic resin.